Contact-point.



. tom view of a can be used and useful JOSEPH A. WILLIAMS, 0F CLEVELAND,

OHIO.

CONTACT-POINT.

Macnee.

Specification of Letters Fatent.

Patented Aug.. M., 1191i?.

Application led August 9, 1915. Serial No. `44,506.

To all whom t may concern.'

Be it known that I, JOSEPH A. WILLIAMS, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented a certain new Improvement in Contact-Points, of which the following is a full, clear, and exact description. y

This invention relates to an electrical contact or contact poirt adapted to be employed in various kinds of electrical apparatus, and particularly in vibrators and circuit breakers of ignition apparatus.

The object of this invention is to provide a contact point having a heat resisting nonoXidizable tip united to a base or carrier in Such a way that the contact point is durable, reliable and efficient in action, and can be produced at a less cost and more satisfactorily than heretofore. y

The invention may be briefly summarized as consisting in certain novel details of construction and combinations and arrangements of parts which will be described in the specification and set forth in the appended claims.

In the accompanying sheet of drawings Figure 1 is a side view and Fig. 2 is a botcontact point constructed in accordance with my invention, parts being broken away.

The contact point constructed in accordance with my invention is composed of an element 10 which has a very high fusing temperature and is not easily oxidized, and a base 11 carrying the element 10 and firmly united thereto in the manner hereinafter explained.

For the element or part 10, which for convenience will be termed the arcing element, I prefer to employ tungsten, although some of the other rare metals such as platinum but not so. effectively as tungsten, and for .the base 11 I prefer to employ relatively soft iron preferably in the form of a so-called tack having a neck or shank 11a by which it may be riveted to a support or holder by inserting the neck in the holder and upsetting the same. Both the aroing element and base are preferably, but not necessarily, circular or disk shaped.

' The -contactpoint is formed elements or parts 10Y and l1 principally because any metal or substance such as tungsten which has the necessary highfusion temperature and does not oxidize under the have found that this of the two' heat of an'electric arc, that it cannot in practice be directly united by riveting or the like to the supporting or holding means. Furthermore, for the same reason, z'. e., because of the eXtreme hardness of the material of which the arcing element is composed, in practice it cannot be thoroughly or 1l, except by a brazing or soldering process.

I have found that copper is the best bonding or brazing material for uniting the arcingelement 10 to the base found also that if it is attempted to braze the two elements together by means of copper used in the ordinary way, 'by placing a disk or thin sheet of copper lbetween the two elements and then subjecting the same to a heating process which fuses and causes it to adhere both to the arcing is so exceedingly hard 11, and I have element and to the base, the two elements I are effectively united, but Hows and iashes onto and over the tungsten so that after the bonding is completed and the parts have cooled, various 'parts of the external surface of the tungsten element are the fused copper coated vwith strongly adhering particles of copper. Inasmuch as the eiiiciency and value of a contact point is very much decreased and practically destroyed if the contact point has even a trace of copper adhering to the active or arcing surface or surfaces thereof,

it 1s-l essential that the contact point whose arcing element. is brazed to the base in the manner above stated be subjected to a pickling process, i. e., by placing the same in an acid bath which will dissolve or eat away the copper which adheres to the tungsten. I

from the tungsten, or the major part of the copper, but it has the very serious disadvantage that it eats away the copper from between the tungsten and the base, thus mechanically and electrically weakening the contact point. There are further disadvantages arising from the use of this acid bath or pickling process, and among these might be mentioned, it is expensive and it is diiiicult to subsequently remove the acid which has crept into the crevice or narrow space between the ,arcing element and the base.

' I overcome all the above mentioned disadvantages, z. e., I avoid ent'rely the flashing or flowing of the copper bond onto the tungsten or other arcing element by my in.- vention which will now be described.

does clean the copper ,Infproducing my improved contact point instead of using a sheet or disk of copper' e.

1s. 1n=a liquid statef'whereas the surface of the tungsten or arcing element is dry and simply placed between the two elements to be united,-I coat the base with a thin layer of lccpper 14 preferably by an electroplating rocess. Preferably the .copper 14 is applled to the entire surface of the base in a thin coat less than one-thousandthof an inchein thickness. Then the contact tip or arcing element is'placed on the base thus coated with copper and the two elements are inserted' in a' furnace until the vcopper coat isfused, and this very effectively unites or bonds'the tungsten t0 the base. But there isthis important difference betweenthe results thus obtained and results obtained if the parts/are brazed by simply 'placing a that when the copper isv applied asa thin coat vonto the'base and when the copper isfused, absolu ely none of the copper flows or flashesonto he tungsten, and whenthe contact point is removed from .the furnace the external surface of the tungsten is absolutely clear or free of the copper, and thus the vnecessit for subjectingthecontact point to the pic ling process is entirely eliminated. I iind that the copper which is fused remains and flows solely on the base, some of the cop- A tungsten brazed to a copper plated iron base per running down the shank or neck of the base forming a slight lilletfat the point where the shank joinsthe body ofv the base,

explain why none of the copper flows or liashes onto the arcing element, I believe that it is due toa sort of surface tension wlnch ernsts in the fused copper which entirely covers the base andprevents it fiowing solid, so that there is a much easier path of flow on the base than onto and along the tungsten. However, whether or4 not .the

above theory or explanation is correct is believed to be immaterial, for the fact remains that with my improved contact point when the latter is removed om the furnace, the tungsten does' notjc ntain'any evidence or trace of copper on its external surface, and is ready for use. I- thus eliminate the necessity for the'picklingprbcess and secure a better process.. i l Having-thus described my invention, what Iclaim is:-'- 1 1. A contact point composed of a lpieceof tungsten .brazed to a base by vbr'azing material applied in the form of a coating which covers the portion of the base adapted to receive the contact tions of the base. A

2 .A contact point. composed of a piece of tungsten brazed to a base by brazing material applied in the form of a coating entirely covering the base.,

Vpoint,' and .adjacent por- 3. A contact point composed of a piece of the copper being applied in a thin coating which covers the portion o'f the base adapted base. v Y v In testimony whereof, I hereunto aix my signature.

JosePHA.winnaar-us.`l 

